Left: American hazelnut. Right: European hazelnut.
Photos from NRCS plants database
Two species of hazelnuts are native to Minnesota and the greater Midwest, the American and Beaked hazelnut (Corylus americana and cornuta respectively). These natives produce small but tasty nuts, are adapted to the extreme weather conditions of the region, and are tolerant or resistant to Eastern Filbert Blight (EFB), a fungal disease which threatens the European hazelnut (Corylus avellana), which is the basis of worldwide commercial hazelnut production. In contrast to the American species, European hazelnuts (also called filberts) produce high yields of large commercially desirable nuts, but are highly susceptible to EFB and are not hardy in Minnesota. Hybrids between the native and European hazelnuts combine the nut quality and yield of the European hazelnuts with the hardiness and disease resistance of the natives, and have potential as a new perennial crop for the Upper Midwest. Selected accessions of American hazelnut may have potential in their own right.
Hazelnuts on the Landscape
Long-lived woody perennials such as hazelnuts are likely to be foundation crops for diverse evergreen agricultural systems, with multiple ecological benefits. Their deep fibrous root systems hold soil in place and reduce leaching, thereby preventing soil erosion and protecting water quality, both from sediments and nutrients. They photosynthesize for a greater portion of the year than annual plants, thereby increasing carbon sequestration and supporting more resilient soil ecology. They also provide habitat for wildlife.
Because they are suited to both small and large scale production, hazelnuts can be fit into many small niches in the agricultural landscape. They add economic value to windbreaks, shelterbelts, and living snow fences (where their bushy growth form makes them especially valuable), wetland and riparian buffers, contour strips, CRP and other marginal land. They make it profitable for farmers to retire from annual agriculture those portions of agricultural landscapes that are least suited to it and which contribute the most to environmental degradation, such as steep slopes and areas prone to flooding. Because they are less sensitive to drought and flooding than annual crops, because they have lower requirements for tillage, fertilizers, and pesticides, and because the timeliness of most management practices is not critical, they enhance the resilience of farmers facing increasing uncertainty in the face of threats such as climate variability.
Our long term goal is to develop a hazelnut industry in Minnesota. To do that we need to 1) develop selected lines of hybrid and native hazelnuts with consistently high nut yield and desirable nut characteristics; 2) develop commercially viable methods of clonal propagation; 3) develop agronomic recommendations for growing them; and 4) develop mechanical harvest and processing equipment as well as markets. Since our first Strategic Planning Meeting of hazelnut stakeholders in October 2007, we have made progress towards this goal with a succession of small public grants. In 2011, a five year USDA-NIFA Specialty Crop Research Initiative Grant, split between Minnesota and four entities in Wisconsin, gave us a solid footing. That grant was not renewed in 2016. Currently we are funded by state-level Forever Green and Minnesota Department of Agriculture Crops Research Grants. The long breeding cycle required for long-lived perennial crops, which is seventeen years for hazelnuts) demands even longer-term funding. The security of long-term funding would enable the U of MN to hire additional staff dedicated to seeing the development of this promising crop through to fruition.
The major obstacle to adoption of hazelnuts in the Upper Midwest is lack of consistently high performing germplasm. Although hybrid hazelnut seedlings have been planted on more than 130 farms in this region (Minnesota, Wisconsin, Iowa, and the Dakotas) since the early 1990s, these have been almost entirely seed-propagated from open-pollinated stock. This means that that the superior genetics responsible for the outstanding yields found in some individuals are not consistently passed on to their progeny. A few progeny may be like their parents or better; however, most will be inferior. More uniformity and predictability is needed if hazelnuts are to become a commercially viable crop, and that can be achieved only through vegetative propagation. Moreover, evaluation of parent material for the currently available planting stock has not been replicated, and thus parents assumed to have outstanding characteristics may have been selected due to locally favorable environmental conditions rather than due to outstanding genetics.
Hazelnut accessions under evaluation
Starting in 2008, researchers at the University of Minnesota (U of M), and their colleagues at the University of Wisconsin (UW), started work to improve hazelnut germplasm adapted to the region. They first identified the best individual bushes from existing plantings of hybrid hazelnuts in the region, then they propagated them by mound layering (a low tech method of vegetative propagation), and planted the resulting clones into five replicated performance trials for long term evaluation under controlled conditions. Over 170 accessions are now represented in these trials, with new ones added every year, including accessions of pure American hazelnut selected from the wild. With up to six years of yield data from these replicated trials, we have now identified eight promising candidates which we hope to propagate and get into more extensive replicated trials on farms in fall 2018.
Three years of yield data have now been collected on the oldest accessions and 19 have been selected for further testing. Those that prove to have consistently high yields, acceptable nut quality and durable resistance to EFB, will be selected for mass propagation for release to growers as improved varieties with relatively uniform plant architecture, maturation date, and nut quality. Concurrently with this, we are crossing the best selections with germplasm from the hazelnut breeding programs at Rutgers in New Jersey and at Oregon State, to introduce traits needed for even better varieties.
Hazelnut hardwood stem cuttings
An essential component in the germplasm improvement work is development of commercially viable methods of mass vegetative propagation. The method that has been used to produce clones for use in the germplasm performance trials, mound layering, is relatively reliable, but highly inefficient, capable of producing only one or two dozen new clones per year. More productive vegetative propagation methods will be needed to produce enough clones of improved varieties to make a difference on the landscape.
The most promising method is by micropropagation, which can produce thousands of new plants within a season. However, hybrid and American hazelnuts are proving to be difficult to micropropagate. The first challenge is in getting micropropagated shoots to form roots.
Left: Hazelnut micropropagation; photo by Jerry Cohen. Center: Research Assistant Molly Kreiser doing micropropagation in the lab. Right: Hazel shoot culture; photo by Brent McCown.
A U of M doctoral student is investigating changes in auxin metabolism regulating adventitious rooting and the role of endogenous indole-3-butyric acid, the plant growth regulator applied to promote rooting, in root formation.
The second challenge is getting micropropagated plants to survive the transition from in-vitro to ex-vitro conditions. A post doc is taking a metabolomics approach to identify conditions eliciting stress responses in the plants during their acclimation to ex vitro conditions. By monitoring metabolites that increase or decrease in abundance in response to certain stresses, she hopes to pinpoint the sources of stress so as to design systems to better avoid them.
One of the challenges of developing a new crop is that agronomic systems and technologies must be worked out concurrently with crop genetics and propagation. Much basic production information is unknown, such as optimal plant spacing, fertilization, weed control and pruning requirements. Some of these may influence determinations about genetics. For example, the best germplasm for dense plantings may not be the same as the best germplasm for widely spaced plantings. Initial attempts to answer these questions were confounded by variable genetics within research trials but new trials using clonal material with the genetic uniformity needed are now underway. Preliminary results show a strong positive response to weed control, but only a weak response to nitrogen fertilization and only under some conditions.
Nowhere is the interaction between technology and genetics more apparent than in harvest and nut processing. Whereas European hazelnuts are trees and are harvested by sweeping the nuts off the ground below them, hazelnuts in the Midwest are bushes (which have more value for windbreaks and erosion control than trees), and thus are harvested by picking the nut clusters directly from the stems. Over-the-top blueberry harvesters work, but improvements can be made; their design may influence choices about aspects such as how strongly nut clusters are attached to stems. Likewise, shelling technology may determine what nut shell characteristics are most desirable. Post-harvest handling of nuts harvested in the husks, which are green and moist at harvest time, will also be different than for European hazelnuts. U. of M. food scientists are currently determining the effects of temperature and humidity on components of nut quality, including rancidity and flavor, during processing and storage to develop recommendations for growers and processors. Information about flavor may also help breeders select germplasm with superior culinary properties, which would give Midwestern hazelnuts a competitive advantage in the marketplace.
Hazelnuts have strong market potential: their nuts may be eaten directly, used as an ingredient in healthy processed foods, or pressed into oil with properties similar to olive oil, with both culinary and cosmetic uses. These markets are likely to grow as appreciation of the health value of tree nuts increases: they are high in heart-healthy monounsaturated fatty acids, vitamin E, thiamin and fiber. The market for hazelnut oil is particularly promising. The nuts average 65% oil, compared to 20% oil for soybeans; so hazelnuts could potentially produce twice as much oil per acre as soybeans.
Left: Bottles of hazelnut oil. Right: Bowl of shelled hazelnuts.
A challenge in the development of a new crop is marketing. Some growers are currently marketing their nuts on a small scale directly to consumers, but larger markets will be needed if hazelnuts are to become more prevalent on the Minnesota agricultural landscape. Larger markets are difficult to access, however, without production volume, and it is hard to build production capacity without the income from marketing. The Minnesota Hazelnut Foundation (MHF), a group of key Minnesota growers, is considering possible cooperative marketing strategies to pool their production and access larger markets. In 2014, some MHF growers joined Wisconsin growers in forming the American Hazelnut Company (AHC), a processing and marketing partnership started based out of the Culinary Arts Center in Gays Mills, Wisconsin. By owning processing equipment jointly and pooling their hazelnuts, AHC grower-owners share the costs of processing, branding, marketing, and distribution. The AHC is focused on streamlining processing techniques and developing value added products to suit the needs of potential customers.
Hazelnuts for Food and Energy: YouTube video
Hazelnut poster displayed at Green Lands Blue Waters conference in 2013
PDF version of poster
Lois Braun, Researcher, Department of Agronomy and Plant Genetics
Jerry Cohen, Professor, Department of Horticultural Science
Pam Ismail, Associate Professor, Department of Food Science and Nutrition
Molly Kreiser, Research Assistant, Department of Horticultural Science
Devin Peterson, Professor, Department of Food Science and Nutrition
Renata Pincelli-Souza, Post-Doctoral Associate, Department of Horticultural Science
Amanda Sames, Department of Agronomy and Plant Genetics
Tonya Schoenfuss, Associate Professor, Department of Food Science and Nutrition
Catrin Tyl, Post-Doctoral Associate, Department of Food Science and Nutrition
Don Wyse, Professor, Department of Agronomy and Plant Genetics